20231221 has 4 divisors (see below), whose sum is σ = 20306700. Its totient is φ = 20155744.

The previous prime is 20231203. The next prime is 20231243. The reversal of 20231221 is 12213202.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 10150596 + 10080625 = 3186^2 + 3175^2 .

It is a cyclic number.

It is not a de Polignac number, because 20231221 - 2⁷ = 20231093 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20235221) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 37336 + ... + 37873.

It is an arithmetic number, because the mean of its divisors is an integer number (5076675).

Almost surely, 2^20231221 is an apocalyptic number.

It is an amenable number.

20231221 is a deficient number, since it is larger than the sum of its proper divisors (75479).

20231221 is an equidigital number, since it uses as much as digits as its factorization.

20231221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 75478.

The product of its (nonzero) digits is 48, while the sum is 13.

The square root of 20231221 is about 4497.9129604740. The cubic root of 20231221 is about 272.4838067980.

Adding to 20231221 its reverse (12213202), we get a palindrome (32444423).

The spelling of 20231221 in words is "twenty million, two hundred thirty-one thousand, two hundred twenty-one".